1. Field of the Invention
The present invention relates to technology for improving transient response characteristics of supercharged pressure in an engine equipped with a charger and a throttle valve of which opening degree is electronically controlled.
2. Related Art of the Invention
There has heretofore been proposed a device for controlling an intake air amount by an engine equipped with a throttle valve of which opening degree is electronically controlled as disclosed in, for example, Japanese Unexamined Patent Publication No. 62-110536.
According to this device, the throttle valve is controlled by calculating a target torque of the engine based upon an accelerator opening degree and an engine rotational speed, and calculating a target throttle valve opening degree based upon the above target torque and the engine rotational speed to obtain a target intake air amount.
In electronically controlling the throttle valve of the engine equipped with a charger for supercharging intake air, it is possible to adjust the target throttle valve opening degree for the target intake air amount corresponding to the supercharged pressure that is variably controlled depending upon the operation conditions, which, however, is not enough for quickly changing the intake air amount due to a delay in the change of the supercharged pressure during the transient period in which the supercharged pressure is changing depending upon a change in the operation conditions. Therefore, it is not possible to control the intake air amount to meet the requirement. In an engine in which the stratified charge combustion and the homogeneous combustion are changed over to each other depending upon the operation conditions, in particular, the supercharged pressure for producing the same torque differs depending upon the respective combustions, giving the occurrence of a torque difference at the time of changing over the combustion.